Consider first a broad overview of the state of the general art to which the present invention relates. In typical underground storage and distribution systems for hazardous fluids such as hydrocarbon fuels, the fuels are usually stored in a large storage tank buried in the ground and delivered through underground piping to delivery pumps or the like. These systems sometimes include a so-called back fill retainer which is simply a round elongated tubular cylinder made of steel which is installed around the pumps and under the street access manhole to maintain back fill materials away from the pump and various plumbing connections.
In recent years there has been an increasing awareness that these primary storage and distribution systems of hazardous fluids need to be contained to prevent product from leaking into the environment to prevent environmental problems such as contamination of public drinking water and making some of the food supply unusable as well as other serious environmental consequences. The Federal Environmental Protection Agency (EPA) has focused on this problem prompting passage of federal and state laws requiring improved means of storage, distribution and leak detection for all stored fluids which are characterized as hazardous. An EPA study concluded that these systems present a hazard to the environment because of poor installation practices, corrosion and structural failures producing leaks contaminating the environment. These laws and regulations have given rise to so-called "secondary containment" systems which essentially provide a second barrier of protection around the primary fluid supply storage and delivery systems.
The secondary containment systems have included access sumps which are an offshoot from the so-called back fill retainer. There are a variety of sumps now on the market usually comprising a base defining an enlarged chamber, a riser connected to the base of smaller diameter and a cover fitting over the top end of the riser which, in some instances, has access openings enclosed by an access lid which provide a means for inspecting the interior of the sump chambers.
These sumps are made from a variety of materials. However, a preferred material is a non-corrodible fiberglass material which is believed to provide advantages over metal containers made of coated steel. These sumps usually house pumps and are usually located at the lowest point of a sloped secondary piping system and thus are a focus of the collection of leaked fluids. These sumps are viewed as a multipurpose chambers and are commonly referred to as "pump access sumps".
Even though the secondary containment systems and detecting means have improved considerably over a relatively short period of time in response to continuously changing environmental and safety regulations and laws, there are still certain component parts and design concepts of these secondary containment systems discussed above which do not provide the optimum solution in developing more fail safe secondary containment systems. For example, even though seals have been utilized between the lip of the sump cover and the top of the riser adjacent the open end, these seals have not proven adequate under extreme conditions to provide a truly water tight or hermetic sump chamber. For example, in areas where the water table is high, the external pressure on the riser often results in a breakage of the seal and migration of fluids into the sump chamber which, of course, is undesirable. Further, the risers are usually of a relatively large diameter and it is difficult to mold fiberglass or polyethylene in a manner to provide a high degree of concentricity between the cover and the riser while still maintaining the economies required for these sump assemblies. It has been found that a certain degree of warpage producing some measure of "out-of-round" is inherent in the manufacturing process.
Consider now more specifically the state of the art. In recent years there has been a public mandate for the protection of our ground water resources. This action has resulted in the Federal Environmental Protection Agency (EPA) issuing strict guidelines for the storage and handling of hazardous liquids. State and local regulatory bodies have also issued regulations which are equal to, or stricter than, those issued by the EPA. Contained within the broad range of regulations are specific requirements that underground pumps and piping connections be provided with a means of secondary containment whereby any leaks in these plumbing connections will be contained and detected by means of a leak sensing device.
As a result of these new regulations, large containment containers have been introduced to the marked called "containment sumps". These multi-purpose containment sumps are typically installed under a conventional street access manhole cover, and are connected at the base to the top of an underground storage tank. The primary function of these containment sumps is to provide a means of secondary containment of the underground storage tanks, submersible pumps, valves, and associated pipe connections. They also serve as a means of keeping back the surrounding ground backfill material and providing a dry working area for routine maintenance and repair. These containment sumps require liquid-tight piping and conduit entries, base and riser connections, and access covers in order to prevent any leaking liquids from escaping, and a means of keeping ground water from entering.
The first containment sumps introduced to the market in the middle 1980's were very limited in design and did not prove to be completely liquid tight. These early models were usually made of fiberglass or corrosion protected steel. Because of the materials used and their design, they were not height adjustable, were difficult to field install and fabricate and provided restrictive pipe and conduit entry capabilities. The one piece construction made the pump and piping installation difficult. Sumps made of coated steel were unpopular because of their potential to fail due to corrosion. The sumps made of rigid fiberglass and steel achieved limited success in providing a liquid tight access cover by means of bolt fasteners and gaskets.
In an effort to provide a containment sump which was easier to install and fabricate, polyethylene containment sumps were introduced in the late 1980's. The sumps were of a two-piece construction with a base section and a height adjustable riser section. This design allowed the tank's pump and plumbing connections to be easily installed into the accessible base section before the upper riser section was installed.
The upper riser section was sized in diameter to be installed inside the lower backfill retainer skirt of the street access manhole. This was a significant improvement because it allowed the sump to move up or down in the manhole skirt during skirt or tank movement, therefore not damaging the sump or the underground storage tank situated under the sump.
The upper riser section was capable of being cut to the required installed height. This height adjustability feature allowed for both deep and shallow tank burial depths. The problem with this two piece base/riser design was that it introduced a new, additional sump connection joint which also had to be liquid tight.
The first polyethylene containment sumps on the market did not have an effective means of sealing the base/riser joint. One such type of two piece sump required that the joint where the riser section made contact with the base section be sealed by means of "speed tip welding". This thermo-plastic welding process required the use of a hot air gun fitted with a special tip on its nozzle which allowed a plastic polyethylene rod to be inserted through an opening in the tip, heated and then melted over the joint area. This welding process proved in the field to be ineffective for untrained personnel. The speed of welding, surface preparation, moisture, and other factors resulted in poor welding applications leading to numerous leaks.
In early 1990 a new sump was introduced to the market to solve the riser/base seal process. This new sump introduced a mechanical means of sealing the riser/base joint by using metal fasteners and a rubber O-ring seal. This required the base of the riser section and the top of the base section to have two inwardly turned flanges with a series of equally spaced bolt holes in both flanges. The rubber O-ring seal was inserted between the bottom portion of the riser flange and the top portion of the base flange on the outside of the fasteners, and they were compressed together by tightening the metal fasteners.
Between 1985 and 1990 another problem with underground containment sumps was beginning to surface. Pipe and conduit entries were difficult and ineffective to seal to the side wall of the containment sump. As a result many containment sumps began to take on water through these ineffectively sealed entries.
Containment sumps which provided fixed pipe and conduit entry locations, such as inwardly and outwardly facing cuffs, proved not to be installation friendly for the installing contractor who was restricted to certain locations for making his pipe and conduit entries. These nonflexible sealed entries not only did not allow the pipe or conduit to accommodate ground movement but they were also ineffective in providing a liquid-tight seal.
Other types of pipe and conduit entry seals were introduced such as a rubber grommet. These seals also failed to be liquid tight because they could not effectively seal angled pipe and conduit entries into the side wall of the containment sump. Additional problems arose such as sealing to a non-flat wall surface, for example in round sumps.
A new product was introduced to the market called a "flexible entry boot" which solved the problem of leaking pipe and conduit entries. This rubber entry boot included mechanical fasteners and was bolted into the side wall of the containment sump. Other design features permitted angled pipe and conduit entries, and they could be installed at any location on the sump's base wall.
After years of improvements made to containment sumps such as ease of installation, height adjustability, and increased liquid-tight seals at the base to tank connection, riser to base connection and the pipe and conduit entry connections, there is but one leakage source problem with which to contend. The access cover has proven to be a major source of water infiltration in high ground water installations.
Recent solutions to this problem have been to install a rubber seal to the top outside circumference of the riser section. Placing the larger diameter overlapping cover over this riser, with a rubber seal installed, provided only a limited amount of sealing protection. Another access cover sealing method using a number of rubber top latches to hold the cover down compressing an O-ring seal, has also proven ineffective. More recently a newly designed sump was introduced to the market which features a bolt-down access cover configuration using metal fasteners and a rubber O-ring. This method of sealing has proven to be effective but requires two flanges: one outwardly facing flange on the bottom of the access cover; and one inwardly facing flange on the top of the riser section. The disadvantage of this type of sump/access cover arrangement is that it is time consuming to remove and replace all of these fasteners each time entry is made into the containment sump. Another problem with this type of sump/access cover arrangement is that the riser section is no longer height adjustable because of the required inwardly facing flange located at the top of the riser section.
A new and improved solution to the problem of leaking containment sump access cover is stated in the description of the following invention.